When a device such as a semiconductor device is manufactured, a film is formed on an object to be processed (“processed object”). As a method of forming a film, a plasma enhanced-atomic layer deposition (“PE-ALD”) method has attracted attention in recent years. For example, Japanese Patent Application Laid-Open No. 2006-278497 discloses a PE-ALD method.
The PE-ALD method disclosed in Japanese Patent Application Laid-Open No. 2006-278497 forms a nitride film. Specifically, the PE-ALD method disclosed in Japanese Patent Application Laid-Open No. 2006-278497 includes supplying dichlorosilane into a reaction tube in which a wafer is accommodated (step 1), supplying hydrogen radicals into the reaction tube (step 2), and then supplying ammonia radicals into the reaction tube (step 3). In the PE-ALD method, step 1, step 2, and step 3 are sequentially performed at each of plural cycles. According to the PE-ALD method, a dichlorosilane based reactant is adsorbed onto the wafer in step 1 and hydrogen is substituted for chlorine included in the reactant in step 2 and a nitriding treatment is performed in step S3. Therefore, a nitride film of high quality, that is, a nitride film with a small wet etching rate ratio (“WERR”) is small, may be formed. In the meantime, the WERR is a scale of quality of a film to be evaluated and a ratio of a wet etching rate of a film to be evaluated by hydrofluoric acid with respect to a wet etching rate of a thermally oxidized film by hydrofluoric acid. When a film to be evaluated has a small WERR, the film is evaluated as a film of high quality.